In current machines and systems communication systems such as, e.g., Ethernet-based networks or field busses are used dependent of the extent of the systems and on the degree of automatization and which connect the decentral I/O devices (input-output devices such as, e.g., sensors and/or actors) and controls. For the transmission of safety-relevant data, safe communication protocols are used as a rule.
Therefore, if it is ensured by suitable measures that a certain safety function is effectively met by a system but also by an individual subscriber such as, e.g., a server, control, I/O devices up to and including an individual hardware and/or software component, this system and/or the individual subscriber or the particular component is considered in the framework of the following specification and of the claims as safe or directed toward safety. If there are no safety-related or safety directed requirements for a system but also for an individual subscriber or for an individual component and if the meeting of a certain safety function is not ensured by suitable measures for the system or the subscriber or the component, this system, the particular subscriber or the particular component is considered as not safe in the framework of the following specification and of the claims.
The concept “safe” or “safety” accordingly concerns in the framework of the invention and in the specification and the claims, unless otherwise indicated, the functional safety.
From the aforementioned therefore, is to be delimited e.g., an electrical safety/security or a secure communication channel in which the security in this connection consists in that the communication channel is secured against unauthorized accesses, or secure data in which the security in this connection consists in that the data is secured against unauthorized reading safe.
Safe network protocols are standardized today, e.g., in the IEC 61784-3. It describes different safety profiles based on principles of a safe network communication. All these network protocols must control the different error models such as, e.g., a mixing of safe and unsafe data and/or telegrams and/or a falsification, loss, delay, exchange, repetition, insertion, and so forth of data and/or telegrams. They define error-recognizing and error-controlling measures with knowledge of the standard network protocol supporting them, e.g., according to fieldbus-based or Ethernet-based communication standards and the error models possible in these networks. The so-called “black channel principle” is frequently used for this. In it, a safety protocol is customarily integrated between a safe use and a “non-safe” standard communication channel which protocol corresponds to the safe level of a safe-directed system and recognizes and controls transmission errors of the communication layers underneath them. That is, the “non-safe” transmission channel is constantly monitored for its integrity by a superposed “safe” protocol. The standardized safe protocols share the fact that they describe the safe communication within a clearly defined and delimited, closed network space. Therefore, there are, e.g., restrictions on the number and the distribution of the standards of the safe network subscribers.